Target location by tracking of imaging device

ABSTRACT

A method and apparatus for tracking a target by tracking the location of an imaging device while the imaging device is tracking the target is described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/214,885, filed Jun. 19, 2008, which claims the benefit of U.S.Provisional Patent Application No. 60/936,388, filed Jun. 19, 2007, bothof which are hereby incorporated by reference herein.

TECHNICAL FIELD

Embodiments of the present invention relate to the field of radiationtreatment, and in particular, to a system of tracking the movement of apathological anatomy during respiration.

BACKGROUND

One challenge facing the delivery of radiation to treat pathologicalanatomies such as tumors or lesions is identifying the location of thetarget (i.e. tumor location within a patient). The most common techniquecurrently used to identify and target a tumor location for treatmentinvolves a diagnostic X-ray or fluoroscopy system to image the patient'sbody to detect the position of the tumor. This technique assumes thatthe tumor is stationary. Even if a patient is kept motionless, radiationtreatment requires additional methods to account for movement due torespiration, in particular when treating a tumor located near the lungs.Breath hold and respiratory gating are two conventional methods used tocompensate for target movement during respiration while a patient isreceiving conventional radiation treatments.

Breath hold requires the patient to hold his or her breath at the samepoint in the breathing cycle and only treats the tumor when the tumor isstationary. A respirometer is often used to measure the tidal volume andensure the breath is being held at the same location in the breathingcycle during each irradiation. Such a breath hold method takes longerthan a standard treatment and often requires training the patient tohold his or her breath in a repeatable manner.

Respiratory gating is the process of turning on the radiation beam as afunction of a patient's breathing cycle. When using a respiratory gatingtechnique, treatment is synchronized to the individual's breathingpattern, limiting the radiation beam delivery to only one specific partof the breathing cycle and targeting the tumor only when it is in theoptimum range. Such a respiratory gating method requires the patient tohave many sessions of training and many days of practice to breathe inthe same manner for long periods of time. A system implementing therespiratory gating method may also require healthy tissue to beirradiated before and after the tumor passes into view to ensurecomplete coverage of the tumor.

Attempts have been made to avoid the burdens placed on a patient frombreath hold and respiratory gating techniques. Some methods for trackingthe movement of a tumor or other target use imaging devices to capturethe internal structure of a patient's body. One imaging modality that iscommonly used in medical applications is ultrasound. Ultrasound systemscreate images of internal structure by detecting reflection signaturesresulting from the propagation of high-frequency sound waves into theinternal structure.

Conventional ultrasound systems are not suitable for use in targettracking applications because the imaging field of such systems istypically small, so that tissue movement affecting the imaged area ismore likely to move a target out of the imaging field. Furthermore,repositioning of the ultrasound transducer to maintain image quality mayrequire intervention by an operator whose presence in a treatment roommay be disruptive, particularly during a treatment session.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings.

FIG. 1 illustrates a system for tracking motion of a target within thebody of a patient and delivering treatment to the tracked target,according to one embodiment of the invention.

FIG. 2 illustrates components of a target tracking system, according toone embodiment of the invention.

FIG. 3 illustrates a target tracking system utilizing an imaging deviceattached to a robotic arm, according to one embodiment of the invention.

FIG. 4 illustrates an ultrasonic imaging system that can be used as animaging device, according to one embodiment of the invention.

FIG. 5 is a flow diagram illustrating a process for administeringradiation treatment while tracking the treatment target according to oneembodiment of the invention.

FIG. 6 is a flow diagram illustrating a process for tracking a target,according to one embodiment of the invention.

DETAILED DESCRIPTION

Described herein is a method and apparatus for tracking the movement ofa target such as a pathological anatomy. The following description setsforth numerous specific details such as examples of specific systems,components, methods, and so forth, in order to provide a goodunderstanding of several embodiments of the present invention. It willbe apparent to one skilled in the art, however, that at least someembodiments of the present invention may be practiced without thesespecific details. In other instances, well-known components or methodsare not described in detail or are presented in simple block diagramformat in order to avoid unnecessarily obscuring the present invention.Thus, the specific details set forth are merely exemplary. Particularimplementations may vary from these exemplary details and still becontemplated to be within the spirit and scope of the present invention.

According to one embodiment of the invention, a target location may betracked relative to a global reference point by determining a positionaloffset between the target location and an imaging device, thendetermining a positional offset between the imaging device and theglobal reference point. The positional offsets may then be added todetermine a global offset between the target and the global referencepoint.

The imaging device may be any device capable of locating a target, suchas a tumor, within a patient's body. For example, the imaging device maycapture images of the target using modalities such as X-ray or computedtomography (CT). Generally, imaging refers to the techniques andprocesses used to create images of an object. Medical imaging isconcerned primarily with the creation of images of structures within thehuman body. An imaging device is an apparatus used for creating images.The images can be two-dimensional (2D) or three-dimensional (3D). If theimages are digital, the elements of 2D and 3D images are often referredto as pixels (picture elements) and voxels (volume elements),respectively. The images generally represent a property of the objectand in the case of medical images a property of living tissue or agentsadministered to living tissue such as intravenous, catheter, and orallyadministered dyes, contrast agents and radiopharmaceuticals. Theproperties of living tissue are generally inferred from an observedsignal. Examples of signals include the measurement of the transmissionof x-rays through the body (the basis for projection radiography andx-ray computed tomography), the measurement of the reflection ofultrasound waves transmitted through the body (the basis forultrasonography), and the measurement of gamma rays emitted byradiopharmaceuticals which have been selectively deposited in the body(the basis for nuclear medicine imaging and positron emissiontomography).

In one embodiment, the imaging device may be an ultrasound scanner, andthe location of the tumor may be determined as a positional offsetbetween the tumor and the ultrasound scanner. The ultrasound scanner maythen be tracked by a tracking device such as an X-ray imager, whichdetermines the positional offset between the ultrasound scanner and theX-ray imager. If the offset between the X-ray imager and the globalreference point is known, then the offset between the X-ray imager andthe global reference point, the offset between the X-ray imager and theultrasound scanner, and the offset between the ultrasound scanner andthe target may all be added to determine the offset between the targetand the global reference point.

In a radiation treatment application, the tracked location of the targetmay be used to direct a linear accelerator (LINAC) and/or the treatmentcouch so that the beam of the LINAC intersects the target, which mayidentify a location in a pathological anatomy. In one embodiment, thetarget may be tracked periodically. The LINAC is mounted on a roboticarm that receives the periodically updated location of the target andadjusts the orientation of the LINAC accordingly. Furthermore, thetreatment couch may also receive the periodically updated location ofthe target and adjusted. In this way, the intersection of the LINAC beamwith the target may be maintained for a desired duration of a treatmentsession despite movement of the target caused by factors such asrespiration, heartbeat, or other causes of movement.

In other embodiments of the invention, the tracking device may be anoptical system, such as a camera, or any other device that can determinepositional information. In one embodiment, the tracking device may be anoptical system that tracks the position of the imaging device bydetecting the position of light-emitting diodes (LEDs) situated on theimaging device. Such an optical system may include infrared cameras fordetecting the position of the LEDs, which may emit light in the infraredspectrum. In an alternative embodiment, if the imaging device, such asan ultrasound scanner, is mounted on a robotic arm, then the trackingdevice may be implemented using sensors or mechanical encoders on therobot arm that can determine the position of the imaging device based onthe joint orientations of the robot arm, as discussed below in relationto FIG. 3.

FIG. 1 illustrates a treatment delivery system 100 for deliveringradiation therapy to a target area within a patient according to oneembodiment of the invention. Treatment delivery system 100 includestracking system 110, treatment couch 101, robotic arm 102, and linearaccelerator (LINAC) 103, which is mounted on robotic arm 102. Trackingsystem 110 further includes a processor 111, a tracking device 112, andan imaging device 113. Treatment couch 101 may be designed to support apatient 104. A target 105 within the patient 104 may be the site of apathological anatomy to receive radiation treatment.

The purpose of a radiation treatment session may be to deliver radiationto target 105 by intersecting target 105 with a radiation beam producedby LINAC 103. Target 105 may be moving, for example, as a result ofrespiration or heartbeat of the patient 104. Thus, tracking system 110may be used to track the location of target 105 as it moves so that theintersection of target 105 with the beam of LINAC 103 may be maintained.Tracking system 110 may send positional information identifying thelocation of target 105 to robotic arm 102 so that robotic arm 102 canadjust the position of LINAC 103 to maintain the intersection of theLINAC beam with target 105. In one embodiment, tracking system 110 maysend the location of target 105 continuously to robotic arm 102.Alternatively, the location information may be sent periodically or maybe sent only when the location of target 105 changes. In anotherembodiment, the tracking system 110 may send the positional informationidentifying the location of target 105 to robotic arm 106 of thetreatment couch 101 so that robotic arm 106 can adjust the position ofthe treatment couch 101 to move the target 105 to maintained theintersection with the LINAC beam. Alternatively, both robotic arms 106and 102 may be utilized in conjunction to maintain the intersection ofthe LINAC beam and target.

Tracking system 110 includes processor 111, which may be connected totracking device 112 and imaging device 113. Imaging device 113 may beused to track the location of target 105 relative to imaging device 113.For example, an image captured by imaging device 113 may indicate apositional offset between target 105 and imaging device 113 or anotherreference point, such as a fiducial marker. Imaging device 113 may bemobile, and may be repositioned for such reasons as maintaining imagequality, for registration purposes, or to keep target 105 within animaging field of imaging device 113. Tracking device 112 may then trackthe location of imaging device 113. For example, tracking device 112 maydetermine a positional offset between imaging device 113 and trackingdevice 112 or some other reference point. Information about the locationof target 105 and imaging device 113 can then be sent to processor 111,where a global position of the target 105 may be calculated. Forexample, a global reference point located in the treatment room may beused for identifying the locations of objects within the treatment room.Accordingly, processor 111 may determine the location of the target 105relative to the global reference point using positional data collectedby tracking device 112 and imaging device 113.

FIG. 2 illustrates components of tracking system 110 in greater detail,according to one embodiment where tracking device 112 is an X-rayimaging system. In tracking system 110, X-ray source 220 and X-raydetector 221 are components of the X-ray imaging system operating astracking device 112. It should be noted that although only one X-raydetector panel 221is illustrated in FIG. 2, alternative embodiments mayinclude additional detector panels. X-ray source 220 has a trackingfield 203, where objects located within tracking field 203 may beeffectively tracked. Similarly, imaging device 113 has an imaging field202, where objects within imaging field 202 may be effectively capturedin an image by imaging device 113. Global reference point 201 is alocation that can be used for designating other locations, particularlyin terms of a positional offset between the global reference point 201and the location being designated. A positional offset simply describesthe location of one reference point relative to another reference point.For example, a positional offset in three-dimensional space may berepresented as a vector having x, y, and z components in a Cartesiancoordinate system. The target offset 211 is the positional offsetbetween the imaging device 113 and the target 105. The imaging deviceoffset 212 is the positional offset between the X-ray source 220 and theimaging device 113. The global tracking device offset 213 is thepositional offset between the global reference point 201 and the X-raysource 220. The global target offset is the positional offset betweenthe global reference point 201 and the target 105.

In one embodiment, the global reference point 201 may be the tracking(e.g., imaging) center of tracking device 112, which includes X-raysource 220 and X-ray detector panel 221. Such a tracking center maycoincide with a treatment isocenter, but not necessarily so. It shouldbe noted that global reference point 201 has been positioned away fromthe other figure elements for ease of illustration.

Imaging device 113 may in one embodiment be an ultrasound scanner.Alternatively, imaging device 113 may be some other type of device thatis capable of locating a target, such as an X-ray imager or anelectromagnetic coil array. Imaging device 113 may be positioned so thatthe imaging field 202 of imaging device 113 encompasses target 105. Forexample, if an ultrasound scanner is used as imaging device 113, thetransducer of the ultrasound scanner may be placed against the skin ofpatient 104 near target 105. Alternatively, if another imaging modalitysuch as X-ray imaging is used, imaging device 113 may be placed fartheraway from the patient 104, as long as the position of target 105 maystill be captured by imaging device 113.

Imaging device 113 may operate by capturing an image of target 105. Theimage can then be used to determine the location of target 105 relativeto imaging device 113, which is the target offset 211. For example, thesize, position, and orientation of target 105 as captured in an image byimaging device 113 may indicate the position and orientation of target105 in real space, relative to imaging device 113. The position oftarget 105 may also be determined by reference to surrounding structureshaving known locations captured in an image along with target 105.

X-ray source 220 may be positioned so that tracking field 203 of X-raysource 220 encompasses imaging device 113. In one embodiment, X-raysource 220 is mounted in a fixed position. For example, X-ray source 220may be mounted on a wall or ceiling of a treatment room where aradiation treatment session is taking place. Alternatively, X-ray source220 may be mobile, so that X-ray source 220 can be repositioned tomaintain imaging device 113 within tracking field 203.

X-ray source 220 and X-ray detector panel 221 determine the imagingdevice offset 213, which is the location of imaging device 113 relativeto X-ray source 220. For example, the X-ray source 220 and X-raydetector panel 221 may capture an image of imaging device 113. The size,orientation, and position of imaging device 113 as represented withinthe captured image may indicate the position of imaging device 113relative to X-ray source 220 in real space. The position of imagingdevice 113 may also be determined by reference to other structureshaving known locations captured in an image along with imaging device113.

The global position of the target 105 may be determined by processor111. Specifically, processor 111 may determine the position of thetarget 105 relative to global reference point 201. Processor 111 maybase this calculation on images captured by X-ray source 220 and X-raydetector panel 221, and also from imaging device 113. The image datareceived by processor 111 in one embodiment may be, for example, raw orprocessed image data. Alternatively, the positional offsets of thetarget 105 and the imaging device 113 may be transmitted to theprocessor, if the positional offsets have already been determined fromthe raw data.

The processor 111 can determine the global target offset 210 by addingthe positional offsets, including the target offset 211, the imagingdevice offset 212, and the global tracking device offset 213. Imagingdevice 113 may capture an image of target 105 that may be used todetermine the target offset 211. Tracking device 112 may then capture animage or otherwise collect data that can be used to determine theimaging device offset 212. The global tracking device offset 213 may bedetermined as part of a calibration measurement and may be measured frompart of tracking device 112 such as X-ray source 220. For example, ifX-ray source 220 is mounted in a fixed location, such as on a wall orceiling of the treatment room, the global tracking device offset 213 maybe measured during or after the installation of X-ray source 220. Theglobal tracking device offset 213 may also be determined using otherimaging or tracking devices. For example, if the X-ray source 220 ismovable on a track or rail, sensors on the track or rail may be used toindicate the position of the X-ray source 220. Once the target offset211, imaging device offset 212, and global tracking device offset 213are known, they can be added to determine the global target offset 210.This calculation may be performed by processor 111. The global targetoffset can then be used, for example, to control robotic arm 102 so thata beam of LINAC 103 intersects target 105. In one embodiment, thedetermination of global target offset 210 may be repeated so that theglobal location of target 105 can be continuously or periodicallyupdated. Alternatively, the determination of the global target offset210 may be performed in response to detecting or anticipating movementby target 105.

In other embodiments, a detector panel such as X-ray detector panel 221may not be required. For example, a camera or other optical system inconjunction with light-emitting diodes (LEDs) attached to imaging device113 may be used as tracking device 112. The camera may track imagingdevice 113 by capturing images including the LEDs, without the need fordetector panel 221. Aside from X-ray imagers, cameras, or similarimaging systems, other types of tracking devices can also be used toperform the functions of tracking device 112.

FIG. 3 illustrates a tracking system for tracking a target 105 withinpatient 104 using a robotic arm system according to one embodiment ofthe invention. The tracking system includes a processor 111, an imagingdevice 113, and a robotic arm 301 and determines a global target offset210 by summing a global imaging device offset 311 and a target offset211. Imaging device 113 has an imaging field 202. Objects within theimaging field 202 may be effectively captured in an image by imagingdevice 113. Offsets 210, 211, and 311 may be described by vectors inthree-dimensional space.

Imaging device 113 is mounted on robotic arm 301 so that robotic arm 301can control the movement, orientation, and position of imaging device113. Depending on the type of imaging device 113 being used, robotic arm301 may hold the imaging device 113 at a distance from the target 105 ormay contact a skin surface of patient 104 with imaging device 113. Forexample, if imaging device 113 is an ultrasound scanner, robotic arm 301may position the ultrasound scanner so that its transducer contacts theskin surface of patient 104. Robotic arm 301 may also be used toreposition imaging device 113 so that target 105 remains within theimaging field 202 of imaging device 113. An ultrasound scanner used asimaging device 113, for instance, may have a small imaging field 202such that movement of the patient 104 due to respiration or heartbeatmay tend to move target 105 outside imaging field 202. Thus, robotic arm301 may be used to compensate for the movement of target 105. In oneembodiment, processor 111 may also be used to monitor the imagescaptured by imaging device 113, detect when target 105 is not withinimaging field 202, and direct robotic arm 301 to move imaging device113. Alternatively, the imaging device may be moved according to adefined path. For example, if the movement of target 105 can bedescribed as a periodic pattern, the imaging device may be movedaccording to that pattern. The imaging device may also be moved forregistration purposes. For example, the imaging device may be moved to aknown location in a treatment room so that images captured by theimaging device may be correlated with the known location for calibrationpurposes.

As previously described, imaging device 113 may be used to determinetarget offset 211, which is the position of target 105 relative toimaging device 113. Global imaging device offset 311 may then bedetermined using sensors or other mechanical encoders on robotic arm301. For example, sensors mounted on the joints of robotic arm 301 mayindicate the orientation of each joint. The joint orientations can thenbe used to calculate the position of the imaging device 113 relative toglobal reference point 201. Once the target offset 211 and the globalimaging device offset 311 are known, the global target offset 210 may becalculated by summing the target offset 211 and the global imagingdevice offset 311. This calculation may be performed by processor 111.In one embodiment, processor 111 may receive offsets 211 and 311 fromrobotic arm 301 and imaging device 113. Alternatively, processor 111 maycalculate offsets 211 and 311 from raw data received from robotic arm301 and imaging device 113. Aside from mechanisms such as robotic arm301, imaging device 113 may also be positioned using other types ofpositioning mechanisms.

FIG. 4 illustrates an ultrasonic imaging system that can be positionedusing a belt mechanism, according to one embodiment of the invention.Ultrasonic imaging system 400 may be used as imaging device 113, andincludes an ultrasonic transducer 410 attached to belt 411 at attachmentpoint 412. Belt 411 is then attached to treatment couch 414 by slider413. The transducer 410 is connected through extension link 424 toexternal unit 420, which includes image processor 422 and drivecircuitry 421. External unit 420 is further connected to a monitor 423.Tracking device 112 may be positioned so that tracking field 203encompasses transducer 410, so that tracking device 112 can be used totrack the position of transducer 410.

While patient 430 is lying on treatment couch 414, transducer 410 isheld in place on the skin surface of patient 430 using belt 411.Transducer 410 is attached to belt 411 at attachment point 412, which inone embodiment, can be removed from and reattached to belt 411 so thatthe position of transducer 410 can be adjusted along the x-axis 440.Alternatively, attachment point 412 may be a sliding attachment thatallows repositioning of transducer 410 without removal and reattachment.Belt 411 may also be attached to treatment couch 414 at slider 413.Slider 413 may allow the belt 411 to be repositioned along the length oftreatment couch 414, along the y-axis 441. Alternatively, other types ofrepositioning mechanisms may be used other than a slider. For example,belt 411 may be repositioned by detaching belt 411 and reattaching belt411 at a different location. In other embodiments, belt 411 may not beattached to treatment couch 414.

The belt assembly, including belt 411 attachment point 412, and slider413, keeps transducer 410 in contact with the skin surface of patient430 at a particular location. Transducer 410 may then be used as imagingdevice 113. The location of a target 105 with respect to transducer 410may be determined using an image of the target 105 captured by theultrasonic imaging system 400. The location of transducer 410 withrespect to tracking device 112 may be determined using tracking device112. The global position of the target 105 with respect to the globalreference point 201 can then be determined by adding the appropriateoffsets, as previously described.

Drive circuitry 421 and image processor 422 may be kept apart fromtransducer 410 so that transducer 410 can be more easily repositioned.Thus, drive circuitry 421 and image processor 422 may be kept in anexternal unit 420, which may be a box or other enclosure. Drivecircuitry 421 may be connected to transducer 410 through extension link424 so that drive circuitry 421 can provide the signals to thetransducer 410 required to conduct the ultrasound imaging. Imageprocessor 422 can also be connected to transducer 410 through extensionlink 424 so that image processor 422 can convert the signals receivedfrom the transducer 410 into an image to be displayed on monitor 423.Extension link 424 may be any medium through which signals can betransmitted, such as a cable or a wireless link, while allowingtransducer 410 to be moved independently from external unit 420.

The ultrasonic imaging system 400 may adjust parameters such as gain,transducer pressure, transmit frequency, receive frequency, and dynamicrange in response to input received from other devices. For example,ultrasonic imaging system 400 may adjust its transmit frequency based onan input received from processor 111 requesting such an adjustment. Inaddition, belt 411 of ultrasonic imaging system 400 may include a gelcontainer that is configured to apply gel between the skin surface ofthe patient 430 and the transducer 410. In one embodiment, applicationof the gel can be initiated by a request sent from another device. Forexample, processor 111 may determine that a reapplication of gel wouldimprove the quality of images produced by ultrasonic imaging system 400.Processor 111 can send an input to ultrasonic imaging system 400 toinitiate the application of gel.

FIG. 5 is a flow diagram illustrating a process for administeringradiation treatment while tracking the treatment target according to oneembodiment of the invention. At block 501 of treatment process 500, thetreatment is planned and treatment nodes are calculated. The treatmentplanning may include determining such details as the radiation dosageneeded to complete the treatment or the angles at which the radiationbeam will intersect the target 105. The process may also determine anumber of treatment nodes, which represent spatial locations from whichthe LINAC 103 delivers a radiation beam to the target 105.

At block 502, the patient 104 is aligned for a treatment node. Thepatient 104 may be placed on a treatment couch 101 so that the target105 within patient 104 is positioned to receive a radiation beamdelivered from the treatment node.

With the patient 104 appropriately aligned, the position of an imagingdevice 113 is adjusted in block 503 so that an image produced by theimaging device 113 is of sufficient quality to be used for registrationwith corresponding images, such as CT or X-ray images. For example, anultrasound scanner used as imaging device 113 may be adjusted tomaintain the target 105 within an imaging field of the scanner, or maybe adjusted to maintain an optimal angle for imaging the target 105. Theadjustment of the position of imaging device 113 can be done manually orby an automatic mechanism. For example, the imaging device 113 may beautomatically repositioned based on the location or orientation of thetarget 105 within an image captured by imaging device 113.

Once the position of the imaging device 113 has been adjusted, thelocation of the imaging device 113 is recorded as a node for thecorresponding treatment node designating the position of LINAC 103,according to block 504. In an alternative embodiment, other parametersmay also be recorded with the imaging device node. For example, if theimaging device 113 is an ultrasound scanner, parameters such as gain,transducer pressure, transmit frequency, receive frequency, and dynamicrange may be recorded. The recorded imaging device node parameters maybe stored in any of a number of storage locations. For example, the nodeparameters may be stored in the imaging device itself, in anothercomponent of the treatment delivery system 100, or in a network locationsuch as a Digital Imaging and Communications in Medicine (DICOM)workstation.

In block 505, if additional treatment nodes are pending, executionproceeds back to block 502. Otherwise, if imaging device nodes have beendetermined corresponding to each of the treatment nodes, then executionproceeds to block 506.

At block 506, patient 104 is placed within range of the treatment robot,which includes robotic arm 102 and LINAC 103. For example, patient 104may be placed on treatment couch 101 near enough to LINAC 103 so that abeam of LINAC 103 can intersect target 105.

With the patient 104 in position to receive treatment from LINAC 103,the treatment session can begin. In block 507, the imaging device 113 ispositioned at a recorded imaging device node corresponding to theinitial treatment node. The recorded imaging device node may alsospecify parameters to be used by the imaging device 113, such as gainadjustment, transmit and receive frequency, and dynamic range. Theimaging node location and other parameters are read, and then applied tothe imaging device. In one embodiment, where the imaging device 113 isan ultrasound scanner having a transducer 410 attached to belt 411, thetransducer 410 may be moved to the location of the imaging device nodeby a positioning mechanism attached to the belt 411. Alternatively, ifthe imaging device 113 is attached to a robotic arm 301, then theimaging device 113 may be moved to the imaging device node by therobotic arm 301. The parameters specified in the imaging device node maybe sent to imaging device 113 so that imaging device 113 may adjust itsparameters accordingly. In some embodiments, imaging device 113 may alsoautomatically adjust its parameters in real-time to facilitate real-timetracking of target 105.

In block 508, the position of the imaging device 113 is adjusted tocompensate for movement of target 105 caused by respiration, heartbeat,or other tissue motion of the patient 104. As in block 507, the imagingdevice may be adjusted using a robotic arm or other positioningmechanism. The imaging device 113 is repositioned so that the imagingdevice 113 can capture images of the target 105 suitable forregistration with other corresponding images of the target 105, such asCT or X-ray images. The position of imaging device 113 is adjusted untilthe quality of the images captured by imaging device 113 is acceptablefor registration, according to block 509.

If the quality of the captured images is acceptable for registrationpurposes, then execution proceeds from block 509 to block 510, where thelocation of the target 105 is determined. The location of target 105 maybe determined by using an image captured by imaging device 113 to locatethe target 105 relative to the imaging device 113. In one embodiment,the location of target 105 is tracked relative to imaging device 113 bydetecting the edges of the structures in images captured by imagingdevice 113, identifying edges to be tracked, and tracking the positionof the identified edge as it moves. For example, an ultrasound scannerused as imaging device 113 may determine the location of target 105 bytracking the edges of target 105 as they appear in images captured bythe ultrasound scanner over time. The tracking device 112 can then beused to locate the imaging device 113 relative to a global referencepoint 201. The location of the target 105 relative to the globalreference point can then be determined from the location of target 105relative to the imaging device 113 and the location of the imagingdevice 113 relative to global reference point 201.

At block 511, the location of the target 105 determined at block 510 isused to update the position of LINAC 103 so that the beam of LINAC 103will intersect target 105. With LINAC 103 properly positioned, theradiation beam is delivered to the target 105 in block 512.

At block 513, if treatment nodes are still pending, then executionproceeds back to block 506, where the treatment process continues. Atblock 506, the patient is positioned within range of the treatmentrobot, if necessary. Blocks 506, 507, 508, 509, 510, 511, 512, and 513are then repeated for subsequent treatment nodes until no more treatmentnodes are pending. When no more treatment nodes are pending, thetreatment session ends at block 514.

FIG. 6 is a flow diagram illustrating a process for tracking a targetaccording to one embodiment of the invention. After block 601 of targettracking process 600, the treatment session is in progress. During thetreatment session, block 508 provides for adjustment of imaging device113 to maintain target 105 within imaging field 202 of the imagingdevice 113. The adjustment is to maintain the quality of the imagecaptured by imaging device 113 so that the image can be used to locatetarget 105 or so the image can be registered with other images such asCT or X-ray images. The positional adjustment of imaging device 113 maybe performed by using a mechanical device such as robotic arm 301 tochange the orientation or position of the imaging device 113. In oneembodiment, a feedback mechanism may be used, where the robotic arm 301adjusts the position of imaging device 113 based on an image captured byimaging device 113. For example, if an image captured by imaging device113 shows that the target 105 is approaching a boundary of imaging field202, robotic arm may respond by moving imaging device 113 to keep target105 near the center of imaging field 202. Alternatively, the positionaladjustment of imaging device 113 may be performed manually. For example,if ultrasonic imaging system 400 is used as imaging device 113, theultrasonic transducer 410 may be manually repositioned using slider 413or attachment point 412. If target 105 is already within imaging field202, execution of block 508 may not be necessary, and adjustment ofimaging device 113 may be avoided.

Block 602 provides for tracking the location of target 105 relative toimaging device 113. The tracking is accomplished by using imaging device113 to capture an image of target 105. The position and orientation oftarget 105 within the captured image can then be used to determine thelocation of target 105 relative to imaging device 113. The result ofthis determination is target offset 211.

Block 603 may be executed either in parallel or sequentially with blocks508 and 602. Block 603 provides for determining the position of theimaging device 113 relative to the global reference point 201.Determining the position of the imaging device 113 relative to theglobal reference point 201 may be accomplished by first using thetracking device 112 to determine an imaging device offset 212 betweenthe tracking device 112 and the imaging device 113, then adding theimaging device offset 212 to a global tracking device offset 213 thatindicates an offset between the tracking device 112 and the globalreference point 201. For example, if an optical device such as a camerais used as tracking device 112, then tracking device 112 may be used tocapture an image that includes imaging device 113. The position andorientation of the imaging device 113 relative to the tracking device112 can then be determined by reference to the position and orientationof the imaging device 113 as it appears in the captured image. Theposition of the imaging device 113 relative to the tracking device 112may be represented as imaging device offset 212. The offset between theimaging device 113 and the global reference point 201 can then bedetermined by adding the imaging device offset 212 and the globaltracking device offset 213. The global tracking device offset 213 may bedetermined before the beginning of the treatment session.

Alternatively, if the imaging device 113 is mounted on a device such asrobotic arm 301, positional sensors on robotic arm 301 may be used todetermine the position of imaging device 113 relative to globalreference point 201. The position of the imaging device 113 relative tothe global reference point 201 may be represented as global imagingdevice offset 311.

When blocks 602 and 603 have been completed, execution proceeds to block604, where the position of the target 105 is determined relative to theglobal reference point 201. The position of target 105 relative toglobal reference point 201 is the global target offset 210, which may berepresented as a three-dimensional vector. The global target offset 210may be calculated by adding the target offset 211, as determined inblock 602, and the offset between imaging device 113 and globalreference point 201, as determined in block 603. The resulting globaltarget offset 210 is the offset between the target 105 and the globalreference point 201.

In block 511, the global target offset 210 is used to adjust the beam ofLINAC 103 so that the beam intersects target 105. In one embodiment, theLINAC 103, which is mounted on robotic arm 102, may be repositioned byrobotic arm 102 to maintain an intersection of the LINAC beam withtarget 105. Alternatively, the treatment couch may be repositioned byrobotic arm 106 to maintain an intersection of the LINAC beam withtarget 105, or a combination of both robotic arms 102 and 106 may beused. Global target offset 210, as determined in block 604, is used todetermine how to position LINAC 103 so that the intersection of theLINAC beam with target 105 is maintained.

At block 513, if any treatment nodes are still pending, the treatment isnot completed and execution proceeds back to block 601, where thetreatment session continues. Blocks 508, 602, 603, 604, 511, 512, and513 are thus repeated for successive treatment nodes until the treatmenthas been completed. If no treatment nodes remain pending upon reachingblock 513, then the treatment session ends, at block 514.

Alternatively, treatment delivery system 100 may be a type of systemother than a robotic arm-based system. For example, treatment deliverysystem 100 may be a gantry-based (isocentric) intensity modulatedradiotherapy (IMRT) system. In a gantry based system, a radiation source(e.g., a LINAC) is mounted on the gantry in such a way that it rotatesin a plane corresponding to an axial slice of the patient. Radiation isthen delivered from several positions on the circular plane of rotation.In IMRT, the shape of the radiation beam is defined by a multi-leafcollimator that allows portions of the beam to be blocked, so that theremaining beam incident on the patient has a pre-defined shape. Theresulting system generates arbitrarily shaped radiation beams thatintersect each other at the global reference point to deliver a dosedistribution to the target region. In IMRT planning, the optimizationalgorithm selects subsets of the main beam and determines the amount oftime that the patient should be exposed to each subset, so that theprescribed dose constraints are best met. In one particular embodiment,the gantry-based system may have a gimbaled radiation source headassembly.

It should be noted that the methods and apparatus described herein arenot limited to use only with medical diagnostic imaging and treatment.In alternative embodiments, the methods and apparatus herein may be usedin applications outside of the medical technology field, such asindustrial imaging and non-destructive testing of materials. In suchapplications, for example, “treatment” may refer generally to theeffectuation of an operation controlled by the treatment planningsystem, such as the application of a beam (e.g., radiation, acoustic,etc.) and “target” may refer to a non-anatomical object or area.

Certain embodiments may be implemented as a computer program productthat may include instructions stored on a computer-readable medium.These instructions may be used to program a general-purpose orspecial-purpose processor to perform the described operations. Acomputer-readable medium includes any mechanism for storing ortransmitting information in a form (e.g., software, processingapplication) readable by a computer. The computer-readable medium mayinclude, but is not limited to, magnetic storage medium (e.g., floppydiskette); optical storage medium (e.g., CD-ROM); magneto-opticalstorage medium; read-only memory (ROM); random-access memory (RAM);erasable programmable memory (e.g., EPROM and EEPROM); flash memory; oranother type of medium suitable for storing electronic instructions.

Additionally, some embodiments may be practiced in distributed computingenvironments where the computer-readable medium is stored on and/orexecuted by more than one computer system. In addition, the informationtransferred between computer systems may either be pulled or pushedacross the communication medium connecting the computer systems.

Although the operations of the methods herein are shown and described ina particular order, the order of the operations of each method may bealtered so that certain operations may be performed in an inverse orderor so that certain operation may be performed, at least in part,concurrently with other operations. In another embodiment, instructionsor sub-operations of distinct operations may be in an intermittentand/or alternating manner.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will, however,be evident that various modifications and changes may be made theretowithout departing from the broader spirit and scope of the invention asset forth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense.

1. A method, comprising: tracking a location of a target using animaging device; tracking a location of the imaging device; anddetermining a location of the target relative to an global referencepoint based on the tracked location of the target and the determinedlocation of the imaging device.
 2. The method of claim 1, whereintracking the location of the target comprises determining a positionaloffset between the target and the imaging device.
 3. The method of claim1, wherein tracking a location of the imaging device comprisesdetermining a positional offset between the imaging device and theglobal reference point.
 4. The method of claim 1, wherein the imagingdevice is an ultrasound imager.
 5. The method of claim 4, wherein theultrasound imager comprises: an ultrasonic transducer; an extension linkcoupled with the ultrasonic transducer; and an external unit coupledwith the extension link, wherein the ultrasonic transducer is moveableindependently from the external unit.
 6. The method of claim 1, whereinthe imaging device comprises an optical system.
 7. The method of claim1, wherein tracking the location of the imaging device comprisescapturing an image of the imaging device using a second imaging device.8. The method of claim 7, wherein the second imaging device is an X-rayimager.
 9. The method of claim 1, wherein the imaging device is mountedon a robotic arm capable of motion with at least five degrees offreedom.
 10. The method of claim 9, wherein tracking the location of theimaging device comprises receiving positional information from therobotic arm.
 11. The method of claim 1, wherein the imaging device iscoupled with a treatment couch.
 12. The method of claim 11, furthercomprising applying the imaging device against a skin surface of apatient using a belt coupled with the imaging device.
 13. The method ofclaim 1, further comprising moving the imaging device to maintain thetarget within an imaging field of the imaging device.
 14. The method ofclaim 1, wherein the location of the target relative to the globalreference comprises a global target offset and wherein the methodfurther comprises maintaining an intersection of a beam with the targetusing the global target offset.
 15. The method of claim 14, maintainingthe intersection of the beam with the target using the global targetoffset comprises adjusting at least one of a first robotic arm coupledto a LINAC generating the beam and a second robotic arm coupled to atreatment couch to support a patient having the target.
 16. Anapparatus, comprising: an imaging device configured to track a locationof a target; a tracking device configured to track a location of theimaging device; and a processor coupled with the imaging device and thetracking device, wherein the processor is configured to determine alocation of the target relative to an global reference point based onthe tracked location of the target and the tracked location of theimaging device.
 17. The apparatus of claim 16, wherein the imagingdevice is configured to track the location of the target relative to theimaging device.
 18. The apparatus of claim 16, wherein the trackingdevice is configured to track the location of the imaging devicerelative to the global reference point.
 19. The apparatus of claim 16,wherein the imaging device comprises an optical system.
 20. Theapparatus of claim 16, wherein the imaging device comprises anultrasound imager.
 21. The apparatus of claim 20, wherein the ultrasoundimager comprises: an ultrasonic transducer; an extension link coupledwith the ultrasonic transducer; and an external unit coupled with theextension link, wherein the ultrasonic transducer is moveableindependently from the external unit.
 22. The apparatus of claim 16,wherein the tracking device is an X-ray imager.
 23. The apparatus ofclaim 16, wherein the imaging device is mounted on a robotic arm capableof movement in at least five degrees of freedom.
 24. The apparatus ofclaim 23, wherein the tracking device tracks a location of the imagingdevice by determining a position of the robotic arm.
 25. The apparatusof claim 16, wherein the imaging device is mounted on a belt coupledwith the treatment couch, wherein the belt is configured to hold theimaging device against a skin surface of a patient.
 26. The apparatus ofclaim 25, wherein the belt includes a gel container configured to applygel between the imaging device and the skin surface of the patient. 27.The apparatus of claim 16, further comprising a positioning mechanismcoupled with the imaging device, wherein the positioning mechanism isconfigured to maintain the target within an imaging field of the imagingdevice.
 28. The apparatus of claim 16, wherein the location of thetarget relative to the global reference comprises a global target offsetand wherein the apparatus further comprises a linear accelerator (LINAC)coupled to a robotic arm, wherein the processor is coupled to therobotic arm to adjust a position of the LINAC to maintain intersection aLINAC beam with the target.
 29. The apparatus of claim 16, wherein thelocation of the target relative to the global reference comprises aglobal target offset and wherein the apparatus further comprises: aLINAC to generate a beam; and a treatment couch coupled to a roboticarm, and wherein the processor is operatively coupled to the robotic armto adjust a position of the treatment couch to maintain intersection ofthe LINAC beam with the target.
 30. An apparatus, comprising: anultrasonic imager configured to track a location of a target; an X-rayimager configured to track a location of the ultrasonic imager; and aprocessor coupled with the ultrasonic imager and the X-ray imager,wherein the processor is configured to determine a location of thetarget relative to a global reference point based on the trackedlocation of the target and the tracked location of the ultrasonicimager.
 31. The apparatus of claim 30, wherein a transducer of theultrasonic imager is mounted on a belt coupled with a treatment couch,wherein the belt is configured to hold the imaging device against a skinsurface of a patient.
 32. The apparatus of claim 30, wherein thelocation of the target relative to the global reference comprises aglobal target offset and wherein the apparatus further comprises alinear accelerator (LINAC) coupled to a robotic arm, wherein theprocessor is coupled to the robotic arm to adjust a position of theLINAC to maintain intersection a LINAC beam with the target.
 33. Theapparatus of claim 30, wherein the location of the target relative tothe global reference comprises a global target offset and wherein theapparatus further comprises: a LINAC to generate a beam; and a treatmentcouch coupled to a robotic arm, and wherein the processor is operativelycoupled to the robotic arm to adjust a position of the treatment couchto maintain intersection of the LINAC beam with the target.